SAN DIEGO – The euphoria of the San Diego Chargers’ stunning win over the defending Super Bowl champion Indianapolis Colts was replaced by reality Monday.

Two-time NFL rushing champion LaDainian Tomlinson, who has a hyperextended left knee, said he should be able to play in Sunday’s AFC championship game. But the Chargers know quarterback Philip Rivers will be gimpy with a sprained right knee if he’s able to play against the undefeated New England Patriots.

Rivers, listed as questionable, injured the medial collateral ligament in his knee when he landed awkwardly after completing a 56-yard screen pass to Darren Sproles for a touchdown on the final play of the third quarter in Sunday’s 28-24 upset of the Colts.

Coach Norv Turner compared Rivers’ situation with that of tight end Antonio Gates, who dislocated his left big toe in a wild-card win over Tennessee, sat out practice all week and then played against the Colts.

“Right now, it’s probably questionable in terms of playing in the game, but he’s got a chance,” Turner said Monday. “That will be a day-to-day thing and we’ll monitor it as the week goes on.”

Rivers was having tests on the knee and wasn’t available to the media. He completed 14-of-19 passes for 264 yards and three touchdowns against the Colts before leaving.

San Diego had to rely on other backups on Sunday, namely running backs Michael Turner and Darren Sproles.

The Chargers already are huge underdogs against the Patriots, and the injuries won’t make it any easier.

“I’m concerned,” Turner said. “I mean, I’m real concerned. We’re lucky, or we’re fortunate, to have a Darren Sproles, have a Michael Turner, have a Brandon McKinney, but you can only withstand so many hits.

“And obviously Billy played great and went in and did the things he had to. But we’re getting ready to play the best team in the National Football League. We need to rally the troops and get everyone as healthy as we can be. I’ve been saying it since August, we want to be at our best. I hope we haven’t played our best game yet. That’s what we’re trying to get done this week.”